The present invention relates to a method for managing the charging of a rechargeable battery comprising at least one module which includes a pair of electrochemical cells, or to a method for operating a device for managing the charging of a rechargeable battery comprising at least one module which includes a pair of electrochemical cells. The invention also relates to a device for carrying out such a method and to a motor vehicle comprising such a device. The invention further relates to a data medium for carrying out such a method.
It is known to stop the charging of a battery for an electric vehicle when the voltage measured at the terminals of a pair of cells in parallel exceeds a threshold. In view of the risk of overcharging, it is necessary for the charging process to be stopped in this way as reliably as possible. The intrinsic reliability of a voltage sensor used for this measurement, although very good, is not sufficient to guarantee that charging will be stopped in all cases. In some cases, a cell will thus be overcharged. This results in the initiation of parasitic reactions, which may damage the battery and may even destroy the functionality of the battery. What is even more troublesome is that the parasitic reactions may release toxic gases. In addition, if the heat flow produced by the exothermic reactions exceeds the heat flow dissipated by the cells into the surrounding environment, a thermal runaway is thus produced, resulting in the more or less violent destruction of the battery, even if the charging of the battery has been stopped.
As explained before, if charging is stopped by means of a voltage measurement and this measurement is faulty, the charging currents of the battery might not be stopped, or might not be stopped in time. To rule out this possibility, a current solution consists in measuring the voltage by means of two systems that are completely independent and redundant.
In addition, it appears rather worthwhile to define and to use a reliable indicator for detection of the overcharging of cells via the use of a measurement of the temperature of a module so as to stop, in good time, all overcharging current of the battery. This indicator is then used in a logic for detecting overcharge in order to stop the charging process in time. This indicator can be a complement that is independent of a logic for stopping the charging process, said logic being managed by a computer managing the battery.
It has been noted that the direct use of the temperature measurement is not sufficient for the detection of overcharging. Studies have shown that it is not possible to detect, on the basis of a temperature measurement, an overcharging having thermal runaway. In fact, such a strategy would involve the use of low temperature thresholds, which would be contrary to the optimization of the use of the battery and therefore to the availability of the vehicle.
The use of a temperature measurement to stop the charging of a battery is described in the following documents: US200501 37823, JP201 001 6944 and FR29261 65.